Twist Drills are the most common cutter type in the CNC arsenal, and they’re most commonly held in the machine tool via a drill chuck. They can also be held in an ER collet chuck and by various other methods. In this article, we’ll go through all this and show you how to get the best performance from your tool holding solution when it comes to twist drills.
Drill Chuck Types
There are commonly two types of drill chucks–Jacobs Chucks and Keyless Drill Chucks.
Jacobs Chuck (Chuck Key Style)
Jacobs chucks require a key to operate:
Keyless Drill Chuck (Albrecht)
Keyless Drill Chucks were invented in 1908 by the firm Albrecht, and are often referred to as Albrecht chucks. They’re often preferred to Jacobs chucks because no key or wrench is needed. A simple twist of the body tightens the chuck firmly:
Drill Chuck Sizes
Image courtesy of micro-machine-shop…
Drill chucks come in a great variety of sizes from small to large.
Jacobs Chuck Sizes
Courtesy of Jacobs…
Keyless Chuck Sizes
Keyless Drill Chuck Sizes, courtesy of Royal Products…
Mini Drill Chucks, Pin Chucks, and Sensitive Drill Feeds
When drilling small holes, sometimes special chucks and accessories may be required.
The sensitive drill feed is an arbor with spring-loaded extension that can be used to hand feed delicate small twist drills with a smaller chuck:
Sensitive Feeds are useful on manual mills and drill presses, but are seldom used with CNC where exact feeds are easily programmed.
Drill Chucks vs Collet Chucks
Drill Chucks have a number of advantages over collet chucks:
- The drill chuck holds a much wider range of twist drill shank diameters.
- Gripping forces of drill chucks are concentrated on three points and can be much higher than for collet chucks.
In general, if you have a well-made drill chuck, it should be as accurate as a collet chuck and will be more versatile as well as gripping the twist drill more tightly.
Mount a Drill Chuck to Stay on its Taper
I prefer to shrink fit my chucks onto their tapers. I put the chuck in the oven at just under 200 degrees and the arbor in the freezer. After 10-15 minutes, tap them sharply together. The temperature difference ensures a tighter fit.
Remove a Drill Chuck
If your drill chuck is mounted on a machine taper, then you’ll use a drill chuck removal wedge to remove it:
The wedge goes between top of chuck and the flange on the taper to force the two apart. Instructables has a good article on how to approach iit.
Make sure your chuck isn’t threaded on, as a wedge will damage a threaded drill chuck installation.
Handy Chuck Key Holder
It’s hard to see in this photo, but I use a triangular welder’s magnet to hold my chuck key to my drill press so it’s always there:
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Bob is responsible for the development and implementation of the popular G-Wizard CNC Software. Bob is also the founder of CNCCookbook, the largest CNC-related blog on the Internet.